This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Children undergoing stem cell transplantation (SCT) often require parenteral nutrition to provide adequate calories and protein due to severe mucositis and other gastrointestinal complications of the preparative regimen (1). Accurate provision of energy may reduce complications related to overfeeding (2) or underfeeding (3). We hypothesize that changes in body composition during SCT affect resting energy expenditure (REE), and that the standard approach to nutritional management of these patients may lead to overfeeding. We propose a randomized controlled trial to compare the nutritional effects of the standard method of nutritional support with an approach in which energy intake provided matches the resting energy expenditure as measured by indirect calorimetry. Specific Aims: To conduct a randomized, double-blinded controlled clinical trial among pediatric SCT patients comparing two methods of nutritional support: 1) standard of care (the provision of 130-150% of estimated basal energy needs via parenteral nutrition), and 2) an experimental protocol in which energy intake is titrated to match resting energy expenditure as measured by indirect calorimetry. A. Primary 1. To compare the effects of standard vs. titrated nutritional support in pediatric SCT patients on percent body fat, as measured by DXA. 2. To compare the effects of standard vs. titrated nutritional support in pediatric SCT patients on glycemic control and insulin resistance. 3. To measure serial changes in REE over the course of SCT with indirect calorimetry. 4. To correlate anticipated changes in REE with changes in body composition. B. Secondary 1.To measure resumption of oral dietary intake after SCT.